As technology progresses with the condition of chasing after higher video quality of television by users, a digital television signal reception system has been popularized gradually.
Referring to FIG. 1, there is shown a configuration diagram of a conventional digital television signal reception system. As illustrated in the figure, the digital television signal reception system 100 is a system for receiving wireless digital input signal of television channel, the system 100 comprising a low-noise amplifier (LNA) 13, a master receiver 14 and at least one slave receiver 15.
The low-noise amplifier 13 is allowed to receive a down-converted digital input signal of television channel (S-in) via an antenna 11 and a low-noise down converter 12, and amplify the input signal of television channel (S-in) with a constant gain so as to send the amplified input signal of television channel (S-in) to the master receiver 14 and the slave receiver 15, respectively.
The master receiver 14 comprises a first low-noise amplifier 141, a first frequency mixer 142 and a first local oscillator source 143. The master receiver 14 is allowed for fine tuning the gain of the first low-noise amplifier 141, such that the input signal of television channel (S-in) may be amplified again by the first low-noise amplifier 141 with suitable gain. Afterwards, the first frequency mixer 142 is allowed for frequency-mixing the input signal of television channel (S-in) with the first local oscillator source (LO1) 143, so as to generate an output signal of first television channel (S-out1). Then, visual content of television program may be watched through a master television connected to the master receiver 14 by playing the output signal of first television channel (S-out1).
Additionally, the slave receiver 15 comprises a second low-noise amplifier 151, a second frequency mixer 152 and a second local oscillator source 153. The slave receiver 15 is allowed for fine tuning the gain of the second low-noise amplifier 151, such that the input signal of television channel (S-in) may be amplified again by the second low-noise amplifier 151 with suitable gain. Afterwards, the second frequency mixer 152 is allowed for frequency-mixing the input signal of television channel (S-in) with the second local oscillator source (LO2) 153, so as to generate an output signal of second television channel (S-out2). Then, visual content of television program may be watched through a slave television connected to the slave receiver 15 by playing the output signal of second television channel (S-out2). In this case, multiple receivers 14, 15 are provided in the digital television signal reception system 100, such that video of television program may be played for multiple television sets.
In the past, the two receivers 14, 15 are designed as chip components provided with internal low-noise amplifiers 141, 151, respectively, so as to avoid local-oscillator leakage existed between the master receiver 14 and the slave receiver 15. For instance, the first local oscillator source (LO1) 143 of the master receiver 14 is improbable to be leaked to the slave receiver 15 due to isolation of the first low-noise amplifier 141, such that interference of local-oscillator leakage of the master receiver 14 on sensitivity of receiving input signal of television channel via the slave receiver 15 is avoided.
Accordingly, although local-oscillator leakage may be avoided if the two receivers 14, 15 are designed as chip components provided with internal low-noise amplifiers 141, 151, respectively, input signal of television channel must be amplified in two stages with the external low-noise amplifier 13 and the internal low-noise amplifiers 141/151. Then, in the digital television signal reception system 100, multiple low-noise amplifiers 13, 141, 151 may be provided, further increasing much area for circuit layout. Furthermore, the gain of the external low-noise amplifier 13 is often just fixed at a smaller gain (such as, below 5 db), to avoid the input signal of television channel (S-in), amplified by the external low-noise amplifier 13, unable to meet the requirement for linearity. Thereby, it is still possible for a weak input signal of television channel (S-in) unable to meet the requirement of the reception system 100 for signal intensity, even if two-stage amplification is performed thereon.